Taco Bell announced this weekend that tests have ruled out all its ingredients except one — scallions — as a possible source of a harsh strain of E. coli that has sickened more than 60 people in the Northeast.

The green onions had been pulled from the company's 5,800 restaurants nationwide on Wednesday after it said preliminary tests showed scallion samples contained the E. coli strain, and it no longer plans to sell them, said Rob Poetsch, a spokesman for the Irvine, Calif.-based company.

Poetsch said samples from the company's entire menu were collected from multiple restaurants in several states for the independent testing done by Certified Laboratories in Plainview, N.Y.

Scallions from a California farm were considered as the source of the outbreak, although health officials are still investigating. But as a precaution, Taco Bell has switched produce suppliers for the Northeast, even though it has no indication that any of the suppliers were associated with the illness.

"We've taken this health issue very seriously and are extremely concerned for all those who are ill. Our company has moved quickly to safeguard the health of our customers and employees," said Greg Creed, the president of Taco Bell Corp.

Creed also said the company would work to quickly reopen any restaurants that were temporarily closed due to the situation.

The Centers for Disease Control and Prevention has said it expected the number of cases to grow. As of Saturday, the agency had counted 61 confirmed cases in five states, most of them in New Jersey, New York, Pennsylvania and Delaware.

South Carolina reported one case, but health officials there said that their case involved a girl who had stopped at a Taco Bell in Pennsylvania last month while traveling.

A case reported in Utah was still under investigation. It was not immediately known whether the Utah victim had recently been in the Northeast, the CDC reported on its Web site.

Forty-nine of those who got sick were hospitalized, and seven developed a type of kidney failure, the CDC said.

Health officials said symptoms of E. coli infection include bloody diarrhea, abdominal cramps or vomiting, but usually not fever.